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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
OL-2239-03
Chapter3 Configuring Cable Modem Interface Features
Configuring the Upstream Cable Modem Interface
Tip For National Television Standards Committee (NTSC) operations, valid ranges are 5000000 to
42000000 Hz.
Caution Some cable systems cannot reliably transport frequencies near these band edges. The wider the upstream
channel (in MHz), the more difficulty you might have. Enter a center frequency between 20 and 38MHz
if you have difficulty.
Note You can also select a default that does not set a specific fixed value. The CiscouBR7200series software
instructs the cableinterfaces to use this frequency as the center frequency.
Verifying the Upstream Frequency
To verify the current value of the upstream frequency, enter the show controllers cable command for
the upstream port you have just configured:
Router# show controllers cable5/0 u0
Cable5/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps
Spectrum Group is overridden
SNR 33.2560 dB
Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval automatic (60 ms)
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
Note The upstream frequency displayed in the show controllers cable command output might not match the
frequency that you entered when you set the upstream frequency. The CiscouBR7200series CMTS
might select an upstream frequency close to the frequency you entered that offers better performance.
The CiscouBR7200series CMTS selects the closest frequency available.
Perform these steps if you are having difficulty with verification:
Step1 Ensure that the cable connections are not loose or disconnected
Step2 Ensure that the cable interface line card is firmly seated in its chassis slot.
Step3 Ensure that the captive installation screws are tight.
Step4 Verify that you have entered the correct slot and port numbers.
Step5 Verify that you have selected a valid frequency for your router.
Command Purpose
Step1
Router(config-if)# cable upstream usport frequency
up-freq-hz
Enters the fixed center frequency for your upstream
RF carrier in Hz.
Step2
Router(config-if)# no cable upstream usport shutdown
Places the upstream port in the “admin up” state.